Thermotectonic History of the Kluane Ranges and Evolution of the Eastern Denali Fault Zone in Southwestern Yukon, Canada

• Published in: Tectonics (Washington, D.C.) D.C.), 2019-08, Vol.38 (8), p.2983-3010
• Main Authors: McDermott, Robert G., Ault, Alexis K., Caine, Jonathan Saul, Thomson, Stuart N.
• Format: Article
• Language: English
• Subjects: (U‐Th)/He thermochronology; Accretion; Apatite; Cooling; Deformation; Denali fault; Evolution; Exhumation; Fault zones; fission‐track thermochronology; Geochronology; Geochronometry; Geological time; strike‐slip fault; Subduction; surface uplift; Tectonic processes; Uplift; Zircon
• ISSN: 0278-7407; 1944-9194
• DOI: 10.1029/2019TC005545

Exhumation and landscape evolution along strike‐slip fault systems reflect tectonic processes that accommodate and partition deformation in orogenic settings. We present 17 new apatite (U‐Th)/He (He), zircon He, apatite fission‐track (FT), and zircon FT dates from the eastern Denali fault zone (EDFZ) that bounds the Kluane Ranges in Yukon, Canada. The dates elucidate patterns of deformation along the EDFZ. Mean apatite He, apatite FT, zircon He, and zircon FT sample dates range within ~26–4, ~110–12, ~94–28, and ~137–83 Ma, respectively. A new zircon U‐Pb date of 113.9 ± 1.7 Ma (2σ) complements existing geochronology and aids in interpretation of low‐temperature thermochronometry data patterns. Samples ≤2 km southwest of the EDFZ trace yield the youngest thermochronometry dates. Multimethod thermochronometry, zircon He date‐effective U patterns, and thermal history modeling reveal rapid cooling ~95–75 Ma, slow cooling ~75–30 Ma, and renewed rapid cooling ~30 Ma to present. The magnitude of net surface uplift constrained by published paleobotanical data, exhumation, and total surface uplift from ~30 Ma to present are ~1, ~2–6, and ~1–7 km, respectively. Exhumation is highest closest to the EDFZ trace but substantially lower than reported for the central Denali fault zone. We infer exhumation and elevation changes associated with ~95–75 Ma terrane accretion and EDFZ activity, relief degradation from ~75–30 Ma, and ~30 Ma to present exhumation and surface uplift as a response to flat‐slab subduction and transpressional deformation. Integrated results reveal new constraints on landscape evolution within the Kluane Ranges directly tied to the EDFZ during the last ~100 Myr. Key Points Thermochronometry documents ~100-Myr thermotectonic history of the eastern Denali fault zone (EDFZ)‐bounded Kluane Ranges, southwest Yukon Data show ~95‐Ma uplift and exhumation, ~70‐ to 30‐Ma relief degradation, and ~30‐Ma uplift and exhumation associated with an evolving EDFZ Post‐30‐Ma surface uplift and exhumation is focused